At a construction site, a conventional cart is generally used for moving a large number of construction materials, such as bricks or bags of cement. The conventional cart includes a carrier and two spaced-apart wheels that are mounted to the carrier. Although the conventional cart is convenient to use, the loaded conventional cart tends to become a heavy burden on a user's arms. In addition, the conventional cart may easily topple over when the loaded conventional cart is moved in a tilted orientation with respect to the ground by an unskilled user. For alleviating the abovementioned deficiencies, another conventional cart disclosed in U.S. Pat. No. 8,413,999 is proposed to provide a rear support mechanism with two spaced-apart rear support wheels that are rollable on the ground. In such a manner, the rear support mechanism with the rear support wheels not only prevents the conventional cart from being easily toppled, but also decreases the burden on the user's arms. However, since the conventional cart is unfoldable, it may occupy a relatively large amount of storage space.